Nucleic Acids Research, 2003, Vol. 31, No. 22 6585-6592
© 2003 Oxford University Press
Article |
p53 stimulates human topoisomerase I activity by modulating its DNA binding
Institute of Molecular Biotechnology, Department of Biochemistry, Beutenbergstrasse 11, D-07745 Jena, Germany
*To whom correspondence should be addressed. Tel +49 3641 656290; Fax +49 3641 656288; Email: kent{at}imb-jena.de
The tumor suppressor protein p53 and the human DNA topoisomerase I (htopoI) interact with each other, which leads to a stimulation of the catalytic activity of htopoI. Moreover, p53 stimulates the topoisomerase I-induced recombination repair (TIRR) reaction. However, little was known about how p53 stimulates this topoisomerase I activity. Here we demonstrate that monomeric p53 is sufficient for the stimulation of the topoisomerase I-catalyzed relaxation activity, but the tetrameric form of p53 is required for the stimulation of TIRR. We also show that p53 stimulates topoisomerase I activity by increasing the dissociation of htopoI from DNA. Since htopoI forms a closed ring structure around the DNA, our results suggest that p53 induces a conformational change within htopoI that results in an opening of the clamp, and thereby releases htopoI from DNA.
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